1. Field of the Invention
This invention relates to a blower unit for an air conditioning system for use in an automotive vehicle.
2. Description of the Prior Art
FIG. 1 schematically shows the construction of a conventional blower unit for an air conditioning system installed on an automotive vehicle.
The blower unit 201 is comprised of a blower unit casing 210 for accommodating a blower 213, two recirculating air intake ports 220A, 220B formed through the blower unit casing 210 for introducing recirculating air A, B, a fresh air intake port 230 formed through the same for introducing fresh air C, a recirculating air intake door 240 for opening/closing the recirculating air intake port 220B, and a recirculating/fresh air intake door 250 for selectively opening/closing the fresh air intake port 230 and the recirculating air intake port 220A.
FIG. 2 is a view showing details of construction of the conventional blower unit, which is also useful for explaining the operation of the same.
The blower unit 201 includes a linkage 260.
The doors 240 and 250 are linked to each other by the linkage 260 and thereby interlocked for opening/closing the recirculating air intake ports 220A, 220B and the fresh air intake port 230.
The linkage 260 is comprised of a driving pivotal lever 261 for transmitting torque to the recirculating/fresh air intake door 250, a driven pivotal lever 262 for transmitting torque to the recirculating air intake door 240, and a rod 263 connecting between the levers 261,262, for transmitting the torque of the driving pivotal lever 261 to the driven pivotal lever 262.
The driving pivotal lever 261 having three ends is supported by a pivot 264 in a manner pivotally movable about the same. The driving pivotal lever 261 has one end connected to the door 250 by a guide block 265 and another end connected to a cable 270 for pushing/pulling the lever 261.
The rod 263 has one end thereof attached to the other end of the driving pivotal lever 261 and the other end thereof attached to one end of the driven pivotal lever 262. The recirculating air intake door 240 is attached to the other end of the driven pivotal lever 262.
The recirculating air intake door 240 and the recirculating/fresh air intake door 250 each pivotally move between two positions indicated by solid lines and a two-dot chain line in a manner interlocked with each other, whereby switching takes place between a recirculating air mode and a fresh air mode.
FIG. 3 shows the relationship between the stroke of the driving pivotal lever (more specifically, the stroke of the other end of the lever 261 connected to the rod 263) and operating angles of the two doors.
In the figure, the ordinate represents the operating angles of the doors 240, 250, while the abscissa represents the stroke of the driving pivotal lever 261. The operating angle of the recirculating/fresh air intake door 250 is represented by a solid line, and that of the recirculating air intake door 240 by a broken line.
When the driving pivotal lever 261 is pulled by the cable 270 to have the other end thereof pivotally moved in a clockwise direction over a predetermined stroke, the recirculating air intake door 250 is pivotally moved in a counterclockwise direction to open the fresh air intake port 230 and at the same time close the recirculating air intake port 220A.
At the same time, the driven pivotal lever 262 is pulled by the rod 263 for rotation in a clockwise direction, whereby the recirculating air intake door 240 is pivotally moved in the same direction to close the other recirculating air intake port 220B.
That is, when the doors 250 and 240 are rotated or pivotally moved to the positions indicated by the respective two-dot chain lines (see FIG. 2), the two recirculating air intake ports 220A, 220B are both completely closed.
Air conditioning units are often shipped with no evaporator or filter mounted therein.
However, if the blower unit 210 is driven without e.g. an evaporator in the air conditioning unit, the airflow is increased by a rate corresponding to pressure loss caused by removal of the evaporator from a space in which it is to be mounted. To preclude this inconvenience, an airflow resistance is created within the system. More specifically, when the evaporator is not mounted in the air conditioning unit, an airflow resistance-creating member (such as a perforated steel plate, a net, etc.) as a substitute for the evaporator is provided in the space where the evaporator is to be mounted to create the airflow resistance on an air outlet side of the blower 213, as disclosed in Japanese Laid-Open Patent Publication No. 5-38928.
However, almost all of such airflow resistance-creating members are discarded after air conditioning units are installed on respective automotive vehicles. This uselessly increases manufacturing costs of the air conditioning system.